#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for(int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("Yes");}else{puts("No");}
#define MAX_N 500005

vector<int> G[MAX_N];

int main() {
    ll n, m;
    cin >> n >> m;
    int b[m], c[m];
    set<int> se;
    rep(i,m){
        cin >> b[i] >> c[i];
        se.insert(b[i]);
        se.insert(c[i]);
    }
    ll ans = n * (n+1) / 2;
    map<int,int> mp;
    int w = se.size();
    int d[w];
    int cnt = 0;
    for(auto x : se){
        mp[x] = cnt;
        d[cnt] = x;
        cnt++;
    }
    rep(i,m){
        b[i] = mp[b[i]];
        c[i] = mp[c[i]];
        G[c[i]].push_back(b[i]);
    }

    int f[w];
    rep(i,w)f[i] = i;
    drep(i,w){
        if(f[i] > i)continue;
        queue<int> que;
        que.push(i);
        while(que.size()){
            int x = que.front();
            que.pop();
            rep(j,G[x].size()){
                int y = G[x][j];
                if(f[y] < i){
                    f[y] = i;
                    que.push(y);
                }
            }
        }
    }

    rep(i,w){
        int x = d[i];
        int y = d[f[i]];
        ans += y - x;
    }

    cout << ans << endl;
    return 0;
}